# CVE-2026-123586: Hickory DNS 0.25.0-alpha.3 through 0.25.2 Query Amplification via Cyclic Referrals

Status: published. Published: 2026-11-08. Updated: 2026-11-08.

Hickory DNS 0.25.0-alpha.3 through 0.25.2 contains a query amplification vulnerability in its recursive resolver, which mishandles cyclic sibling name server referrals that lack glue records. Attackers controlling two zones whose name servers reference each other without glue records can make the recursor loop, sending many upstream queries, amplified further by zero-TTL NS records.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- hickory-dns / hickory-dns (hickory-recursor): ≥ 0.25.0-alpha.3; ≤ 0.25.2 (affected, semver). Source: CNA: VulnCheck
- hickory-dns / hickory-dns (hickory-resolver): ≥ 0; < 0.26.2 (affected, semver); 0.26.2 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-400

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-cx5j-p54p-q756 (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/hickory-dns-0.25.0-alpha.3-through-0.25.2-query-amplification-via-cyclic-referrals (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123586; retrieved 2026-11-08; source updated 2026-11-08

Revision: 46f622c1e7ffd3359af5fb566efa13390c3ec037e359c075e5f515e0c2ae28fc

Canonical: https://y2.dev/cve/CVE-2026-123586

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